Trucks having open rear cargo bays are typically backed into alignment with a loading dock or other doorway of a building to facilitate loading and unloading of the vehicle. A significant gap is usually created between the rear of the truck and the face of the building, which exposes the interiors of the building and the truck to the outside environment during loading and unloading. Such gaps can be at least partially sealed by installing either a loading dock shelter or a loading dock seal around the perimeter of the doorway.
To seal or shelter the vehicle's rear vertical edges, dock shelters and dock seals usually have some type of lateral weather barrier installed along the side edges of the doorway. For dock shelters, the weather barrier usually shelters or seals against the vertical sides of the vehicle's trailer. An example of such an approach is shown in U.S. Pat. No. 3,322,132. Dock seals, on the other hand, usually have lateral weather barriers that are resiliently compressible for conformingly sealing against the vertical rear edges of the vehicle. An example of such an approach is shown in U.S. Pat. No. 5,125,196. Regardless of the structural design of the lateral weather barrier, the upper rear edge of the vehicle is often sealed or sheltered by a head curtain that drapes down onto the top of the vehicle as the vehicle backs into the dock.
If the head curtain is extra long to accommodate a broad range of vehicle heights, the dock shelter or dock seal might include means for vertically retracting the curtain so that the curtain length is appropriate for the height of the particular vehicle at the dock. Thus, the curtain needs to be flexible not only for deflecting in reaction to the vehicle backing into the dock, but also for enabling the curtain to be retracted. Such flexibility or compliance, however, can weaken or hinder the curtain's ability to forcibly seal against the rear upper edge of the vehicle. Thus, instead of the curtain applying sealingly tight pressure against the upper edge of the vehicle, a pliable curtain readily deflects backwards toward the doorway of the dock.